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首页> 外文期刊>Journal of the mechanical behavior of biomedical materials >Fracture mechanisms in Ti and Co-Cr growing rods and impact on clinical practice*
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Fracture mechanisms in Ti and Co-Cr growing rods and impact on clinical practice*

机译：Ti和Co-Cr成长杆的断裂机制和对临床实践的影响*

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摘要

The widely used treatment of early onset scoliosis based on fusionless spinal instrumentation with growing rods suffers from severe complications due to premature rod failure. Only few studies have explored the fracture mechanisms in single rod constructs, while clinical practice urgently needs guidance. The objectives of this study are (i) to determine the failure mechanisms in Ti-6Al-4V alloy, Ti Cp 2 and Co-Cr alloy rods, and (ii) to propose strategies to reduce the risk of rod fracture. For this purpose, seven rods from three patients treated for early onset scoliosis were characterized by preoperative, pre-fracture X-rays and after-fracture X-rays. Fracture surface analysis, performed using scanning electron microscopy, revealed similar failure mechanisms for all rods, independent of composition and diameter. Fracture is caused by fatigue, associated to repeated bending action in the anteroposterior direction. Cracking initiates at multiple sites. Three-point bending fatigue tests on Ti-6Al-4V bent rods confirmed the fracture scenario. A beam bending model indicates that the failure process is controlled by the combination of cyclic vertical and horizontal forces with amplitudes from 200 N to 400 N and from 70 N to 150 N, respectively. Strategies to minimize fracture involve adaptations of material properties and rod geometry to scoliosis characteristics, including sagittal alignment, and spine behavior.
机译：早期脊柱侧凸的广泛治疗基于无融合脊柱内固定器和生长棒，由于棒过早失效，会出现严重并发症。只有少数研究探索了单杆结构的骨折机制，而临床实践迫切需要指导。本研究的目的是（i）确定Ti-6Al-4V合金、Ti-Cp 2和Co-Cr合金杆的失效机制，以及（ii）提出降低杆断裂风险的策略。为此，对三名早发性脊柱侧凸患者的七根脊柱棒进行了术前、骨折前和骨折后X线检查。使用扫描电子显微镜进行的断口分析显示，所有杆件的失效机制相似，与成分和直径无关。骨折是由疲劳引起的，与前后方向的反复弯曲作用有关。在多个位置开始开裂。Ti-6Al-4V弯曲杆的三点弯曲疲劳试验证实了断裂情况。梁弯曲模型表明，破坏过程由振幅分别为200 N至400 N和70 N至150 N的循环垂直力和水平力的组合控制。减少骨折的策略包括根据脊柱侧凸的特点，调整材料特性和杆的几何形状，包括矢状面对齐和脊柱行为。

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